One could write a js-less DOM impl I think.. neither Chrome nor Firefox itself is written in js unlike big parts of Linux that are indeed written in C. Explorer shipped with vbscript as a language that can manipulate the DOM.
The really big issue in this case is network effect, which is why I hope something can come out from the momentum building behind WASM.
One couldn't, because you'd need to standardize a JS-less DOM, which requires one to persuade Apple, Google, Microsoft, and Mozilla to agree on a new standard for a JS-less DOM API.
The DOM API is currently defined as a JS API, including JS strings, JS objects + properties, JS Exceptions, JS Promises, JS garbage collection, and on and on and on.
The effort to get all the browsers to agree to standardize a new JS-less DOM API would take years; none of the browser vendors even want to begin that conversation today.
The really big issue in this case is network effect, which is why I hope something can come out from the momentum building behind WASM.